Marine forearc structure of the 2014 Mw 8.1 Iquique earthquake in Northern Chile revealed by relocated hypocenter locations from offshore observations
Abstract
The North Chilean subduction zone is a unique region to study the influence of postseismic relaxation and active deformation within the marine forearc. The Iquique earthquake ruptured on April 2014 with magnitude 8.1 in the central part of a well-known seismic gap and left two smaller unbroken adjacent segments in northern Chile. This major earthquake and the large amount subsequent aftershock seismicity offer the possibility to study the heterogeneous structure of the marine forearc and to investigate the transition to the remaining unruptured seismic gap. Offshore seismological observations enable to improve land-based investigations toward the trench and provide a more detailed study of potential transient fluid migration into the upper plate of the marine forearc. From December 2014 until November 2016, we deployed two consecutive amphibious seismic networks of 15 Ocean Bottom Seismometers (OBS) that covered the Iquique 2014 rupture area and the adjacent unbroken region to the south. Besides the offshore data we use onshore stations from of the IPOC (Integrated Plate Boundary Observatory Chile) and CSN (Chilean Seismological Service) networks.
We present a high-resolution earthquake catalogue of hypocenter locations detected using a local back-projection method integrated in SeisComP3. Arrival times and their quality estimates were further enhanced with MannekenPix (MPX) picking algorithm for first P-wave arrivals. Additionally, we applied the S-wave picking technique from Diehl et al. 2009 on horizontal components and determined local magnitudes. Furthermore, we calculated double-difference hypocenter relocations based on waveform cross-correlations. Most of the seismicity occurs between 19°S and 21°S up-dip of the maximum coseismic slip of the 2014 mainshock. The seismicity at seismogenic depths is highly focused forming well-defined clusters. The observed seismicity provides constraints on the structure of the marine forearc and the postseismic deformation. We relate the seismicity distribution to the background seismicity, seafloor morphology, and regional tectonics.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T51F0339P
- Keywords:
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- 8045 Role of fluids;
- STRUCTURAL GEOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS;
- 8170 Subduction zone processes;
- TECTONOPHYSICS